Tamed (aka charmed) pet classes are an absolute nightmare to balance -- going all the way back to original EQ, required oft-shifting restrictions and cons (e.g. random charm breaks), and mobs of many types flagged immune. While they could be completely overpowered in an area with potent 'charmable' creatures, the entire mechanic would need to be supplemented with other DPS options for the job in an area where creatures aren't usable as pets.